Patients with jejunal-ileal bypass surgery were evaluated five years post-surgery. Fluorescein angiography and measures of optical density showed a dramatic thinning of the pigment epithelium. Visual acuity, dark adaptation and color vision remained normal. Electroretinography (ERG) showed a significant decrease in the light adapted a wave. A consistent constriction in the red color fields was also demonstrated. These patients continue to manifest normal dark adaptation and normal scoptic ERG despite decreased serum vitamin A levels, indicating normal retinal vitamin A content. Bypass surgery is associated with a developing defect in cone function and a marked thinning of the pigment epithelium unrelated to vitamin A deficiency.